Interpretive Summary: Johne's disease is a chronic, debilitating intestinal disorder in cattle characterized by diarrhea, reduced feed intake, weight loss and death. Cattle usually become infected as young calves by ingesting feces containing the causative bacteria. However, symptoms of disease do not usually present themselves until the animals reach 3 to 5 years of age or even older. During this time the animal is infected and may be shedding the organism in its feces without showing any clinical signs of disease. In addition to reduced milk production by these animals, they also present a potential infective threat to the rest of the herd. Johne’s disease is difficult to diagnose and therefore to control. Development of accurate and sensitive diagnostic tests is dependent upon understanding the immune responses of the host animal during infection. This paper presents data on the expression of genes by T cells of infected animals and compares the results with gene expression by T cells from noninfected control cows during the periparturient period to determine if certain genes are affected by disease and/or calving. Further work on host immunity will lead to better understanding of the pathogenesis of disease and aid in new preventative and therapeutic regimes.

Technical Abstract:
Twenty multiparous and two primiparous Holstein cows were grouped according to infection status with Mycobacterium avium subsp. paratuberculosis (MAP), the causative microorganism for Johne’s disease. The effect of parturition and infection on the progression of Johne’s disease was monitored by determining the expression and secretion of key cytokines. Despite the ability of MAP and parturition to modulate cytokine gene expression, the transition from subclinical to clinical disease state did not occur during the immediate postpartum period.